This study aims to evaluate the feasibility, acceptability and efficacy of transdiagnostic Cognitive Behavioural Therapy (tCBT) in comparison to delayed-treatment for depression and anxiety in older people. CBT is a form of 'talking therapy' that has been recommended by the National Institute of Clinical Excellence for the treatment of mood disorders. While traditional disorder-specific CBT has been found to be effective at alleviating individual mood disorders, it may be less effective when multiple mood disorders are present (i.e. when there is psychological comorbidity). tCBT is a form of CBT that targets cognitive and behavioural processes common to a range of mood disorders. Consequently, it may be better placed to address comorbidity than traditional CBT, both in terms of clinical and cost-effectiveness.